Study On The Synergistic Denitration Performance Of Steel Slag And Activated Carbon

With the increasing stringent national environmental regulations,the NO_x emissions of metallurgical industry will be strictly controlled.At present,some sintering plants of iron and steel industry absorb of SO2,NO_x,dioxins and other harmful gases by using activated carbon.However,the cost of the activated carbon for desulfurization and denitration is high.The iron and steel industry not only discharges high NO_x emission but also generates huge amounts of the solid wastes,such as large accumulation of steel slag but low utilization.There is still a certain amount of iron in the slag which is not used.Many researchers show that the ironbased catalyst has the characteristics of low cost,wide active window,antitoxic ability and the others.It shows a good applied prospect in SCR denitration process by iron-based catalysts.Therefore,we could not only find a new way of utilization of steel slag but also utilize the steel slag and activated carbon for denitration by synergistic catalytic adsorption if the steel slag could be used as the raw material to prepare composite absorbent with activated carbon.Meanwhile,it can reduce the denitration cost of activated carbon and this will be of great significance for practical engineering application.Different kinds of steel slag and coal-based activated carbon samples were collected to prepare the mixture(composite absorbent)with different mixing ratios.An experimental study on the optimum proportion of steel slag and activated carbon in the composite absorbent and the denitration performance of the composite absorbent were conducted in an electric heating quartz glass tube reactor.And the effects of reaction temperature,NO concentration,oxygen concentration and types of steel slag were all considered.Response surface methodology was used to optimize the operating parameters.The experimental study on the composite absorbent prepared by steel slag with different iron content was carried out at the optimum reaction conditions.Meanwhile,the characterization analyses of BET,XRF,SEM and TG were carried out and the mechanism of denitration was also analyzed.The experimental results show that the influence of the reaction temperature and the initial NO concentration on the denitration efficiency of the composite absorbent is negative,and the influence of oxygen content in flue gas on the denitration efficiency of composite absorbent is positive.Based on the response surface method,the results show that the three factors,such as reaction temperature,NO concentration and oxygen content,have significant effects on the efficiency of the absorbent and the interaction of reaction temperature and oxygen content is obvious in the three factors.The optimal operating conditions are as follows,temperature of 116?,O_xygen concentration of 12%,NO concentration of 400 ppm,and the highest efficiency is 72.5%.The verified experimental efficiency of the composite absorbent is 71.4% under the optimum conditions.Through the characterization analyses of activated carbon,steel slag and composite absorbent(i.e.TG,XRF,BET,SEM)the results show that the activated carbon has a certain thermal stability and the elemental iron content is the intrinsic factor which affects the efficiency of the composite absorbent.The preliminary study shows that there are two modes of action in the process of denitration,one is the adsorption of activated carbon and the other is the catalytic reduction of steel slag.